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Study Questions Influence of High-Salt Diet on MS

August 25, 2017

SUMMARY

Some recent studies have suggested that high intake of salt in the diet might influence MS disease activity and progression, but other studies have not confirmed that link.

In work partly funded by the National MS Society, researchers took advantage of data accumulated from a previous clinical trial involving 465 people with possible early signs of MS (CIS) whose salt levels in urine were measured over the course of 5 years.

Although this study does not support a link between high-salt diets and MS disease activity, research suggests that most Americans eat more salt than is recommended by federal guidelines. Reducing dietary salt is considered by most to be beneficial to the heart and circulatory system.

DETAILSBackground: Several recent studies have suggested that dietary salt (sodium chloride) could potentially influence MS disease activity and progression. For example, one study of 70 people with relapsing-remitting MS, who were followed for two years, found that higher levels of salt measured in urine samples were associated with a higher rate of relapses and larger brain MRI lesions. In addition, mice fed a high-salt diet developed a more aggressive course of EAE, a laboratory model of MS. But two studies in pediatric MS did not find a relationship between self-reported salt intake and MS risk or relapse rates. Resolving this question is important because it offers the possibility that reducing salt intake might improve a person’s overall health and their course of MS.

This Study: In work partly funded by the National MS Society, researchers set out to determine if a high-salt diet is associated with faster conversion from a first neurologic episode (known as clinically isolated syndrome or CIS) to a diagnosis of definite multiple sclerosis, or with MS disease activity. Kathryn C. Fitzgerald, ScD (Johns Hopkins School of Medicine), Alberto Ascherio, MD, DrPH (Harvard T. H. Chan School of Public Health) and colleagues took advantage of data accumulated from a previous clinical trial involving 465 participants who participated in a trial called BENEFIT (Betaferon/Betaseron in Newly Emerging Multiple Sclerosis for Initial Treatment) over 5 years. The trial compared benefits of giving interferon to individuals with CIS early versus later. Each person provided an average of 14 urine samples throughout the five-year follow-up. The researchers estimated average long-term sodium intake from the multiple urine samples, adjusting for age, sex, height, weight, where participants lived, and many other variables.

Results: Researchers found that neither average nor high urine sodium levels were associated with conversion to definite MS. They also weren’t associated with new MRI lesions at any point in the five years, relapse rates, or progression of disability. These results suggest that high sodium intake does not play a major role in influencing MS disease course or activity in people treated with interferon, at least in the early stages of the disease.

While the study has several strengths, including its length, large sample size, and systematic collection of data, it has limitations: BENEFIT participants were treated nearly uniformly with interferon, and the results may not apply to people on other therapies or no therapy. In addition, participants in the BENEFIT trial were primarily Caucasian and resided in Europe and Canada, and it isn’t known if similar results would apply to other populations and ethnicities. The results also don’t answer the question of whether salt intake affects the risk of developing MS in the first place.

Comment: Although this study does not support a link between high-salt intake and MS disease activity, research suggests that most Americans eat more salt than is recommended by federal guidelines. Even in the absence of direct evidence that MS immune activity is influenced by salt, reducing dietary salt is considered by most to be beneficial to the heart and circulatory system.

Read More: Diet, along with exercise, cognitive health, and other healthy behaviors can make a big difference to how you feel as you deal with MS. Learn more about living well with MS

About Multiple Sclerosis

Multiple sclerosis is an unpredictable, often disabling disease of the central nervous system that disrupts the flow of information within the brain, and between the brain and body. Symptoms range from numbness and tingling to blindness and paralysis. The progress, severity and specific symptoms of MS in any one person cannot yet be predicted, but advances in research and treatment are leading to better understanding and moving us closer to a world free of MS. Most people with MS are diagnosed between the ages of 20 and 50, with at least two to three times more women than men being diagnosed with the disease. MS affects more than 2.3 million people worldwide.